The present invention relates generally to an intraluminal radiation system for the delivery of treatment elements by way of a catheter to a selected location within the intraluminal passageways of a patient. More particularly, the present invention relates primarily to an improved transfer device for handling the treatment elements and delivering them to the catheter and an improved catheter assembly.
Since the late1970""s balloon angioplasty techniques have become widely used for opening blockages in coronary arteries. Briefly, the enlargement of the artery is achieved by advancing a balloon catheter into a narrowed portion of the artery and inflating the balloon to expand the diameter of the artery, thus opening the artery for greater blood flow. Atherectomy techniques, in which blockages are removed or reduced in size, have also been used to the same end.
While balloon angioplasty has proved an effective way of opening the coronary arteries, in a significant number of cases the arteries will narrow again at the location where the balloon was expanded, such narrowing being termed restenosis. Restenosis is believed to be caused by formation of scar tissue at the site of the angioplasty that results from the injury to the artery caused by the inflation of the balloon. More recently, intraluminal radiation has been used after angioplasty or atherectomy to treat the affected area of the artery to inhibit cell proliferation and wound healing response and, consequently, help to prevent restenosis. Methods and apparatus for such intraluminal radiation treatment are disclosed in U.S. Pat. Nos. 5,899,882, and 6,031,020, filed Sep. 23, 1997, and U.S. Pat. No. 6,261,219, filed May 4, 1999, all of which are incorporated herein by reference. These applications generally disclose an apparatus comprising a catheter, which is inserted intraluminally into the patient and advanced to the site of the area to be treated, and a transfer device for facilitating either the hydraulic or pneumatic advancement and retrieval of individual radioactive treating elements or xe2x80x9cseedsxe2x80x9d along the catheter to and from the treatment site.
As with any device inserted into the vascular system, it must have sufficient integrity to insure that no pieces or elements are separated from or exit the device into the vascular system. This is particularly true for the treating elements which are moved to and from the distal end of the catheter. Additionally, because the device is intended to use radioactive treating elements, there is a heightened need for safety to prevent any unintended exposure of either the patient or the user to radioactivity.
Actual use of the apparatus described in the above-identified patent and co-pending applications has suggested several areas where the device could be improved to reduce the possibility of having treatment elements escape from the system, thus enhancing patient and user safety.
Consequently, it is the principal object of the present invention to provide a transfer device and catheter assembly that has additional safeguards to protect the patient and user for unintended exposure to radiation.
More particularly, it is an object of the present invention to provide a transfer device/catheter assembly in which the treatment elements cannot be inadvertently released from the transfer device.
These objects, as well as others which will become apparent upon reference to the following drawings and detailed description, are provided by a transfer device usable in a system for intraluminal treatment of a selected site in a body of a patient in which the transfer device comprises an integral pump for pressurizing and circulating fluid through a fluid path defined by the transfer device and associated catheter. A removable fluid cartridge is provided including a reservoir from which fluid is drawn by the pump and into which fluid is returned after being circulated through the fluid path. The pump may be a peristaltic pump and the fluid cartridge may include an elongated fluid pickup having an inlet through which fluid is introduced into the transfer device. The fluid pick-up is sized in length so that the inlet is always submerged in the fluid regardless of the orientation of the transfer device. A removable treatment cartridge having a lumen forming part of the fluid path may also be provided, and a storage sleeve for the treatment cartridge may be of a radiation-blocking material, such as quartz. Further, the treatment cartridge may have a memory for storing and indicating selected information about the treating element.
In another aspect of the invention, the transfer device may include a system for preventing operation of the transfer device unless each of the catheter, fluid cartridge and treating or source cartridge are attached to the transfer device. In a preferred embodiment, such a system may comprise an illumination source and an optical sensor located in the transfer device in proximity to where each of the catheter, fluid cartridge, and source cartridge is received by the transfer device. Each illumination source is located with respect to its optical sensor so that the optical sensor is able to receive light from its illumination source only if the catheter, fluid cartridge or source cartridge is not received by the transfer device. The optical sensor is blocked from receiving light from the illumination source when the catheter, fluid cartridge or source cartridge are received by the transfer device. A microprocessor that controls movement of the treating element from the transfer device to the catheter prevents operation of the transfer device upon receiving a signal from any of the optical sensors indicating that at least one of the catheter, fluid cartridge, and source cartridge is not attached to the transfer device.
In a still further aspect of the invention, a catheter is provided for use in the intraluminal treatment system which has four lumens extending substantially along the length of the catheter, one lumen being sized to slidingly receive a treating element and being in fluid communication with two lumens at the distal end thereof for the return of fluid. The fourth lumen is open at the distal end to receive a guidewire. The catheter may have a distal end with a cross-sectional area smaller than the proximal end of the catheter, the cross-sectional shape being non-circular so as to permit perfusion.
In a further aspect of the invention, the transfer device includes a gate movable between first and second positions for selectively permitting or preventing the treating element from moving from the treating element cartridge to the catheter, with an actuator controlling the gate that also permits release of the catheter and the treating element cartridge from the transfer device only when the gate is in position to prevent the treating element from moving from the treating element cartridge to the catheter.
In a further aspect of the invention, the transfer device includes a system for detecting the presence or absence of the treating element in the storage sleeve including a light source disposed on one side of the storage sleeve and a linear array of photosensors disposed on a second side of the storage sleeve. A microprocessor is provided for comparing the amount of light measured by the photosensors to a reference amount corresponding to the amount of light measured by the photosensors when the treating element is not within the lumen of the storage sleeve.